CN114430099B - E-surface terahertz waveguide filter based on novel dual-mode resonant cavity - Google Patents

Abstract

The invention aims to provide an E-surface terahertz waveguide filter based on a novel dual-mode resonant cavity, and belongs to the technical field of terahertz waveguide filters. The waveguide filter is innovatively designed into a dual-mode resonant cavity, the dual-mode resonant cavity is symmetrical about an E surface and an H surface of a waveguide, and meanwhile, the size of the dual-mode resonant cavity meets the requirement that TM120 mode resonance and TE101 mode resonance can be simultaneously excited when electromagnetic wave signals are transmitted in the cavity, and a zero point is introduced through the dual-mode resonance; the height and the width of the cavity can be adjusted, so that the zero position is adjusted, and the out-of-band rejection degree of the out-of-band cavity is increased; in addition, the cavity is simple in structure, the cavity width-depth ratio is small, E-plane machining can be adopted, and machining errors are reduced.

Description

An E-plane THz waveguide filter based on a novel dual-mode resonator

technical field

The invention belongs to the technical field of terahertz waveguide filters, in particular to an E-plane terahertz waveguide filter based on a novel dual-mode resonant cavity.

Background technique

Because the waveguide structure has higher power capacity and smaller insertion loss than the microstrip line and stripline structure, the waveguide cavity structure is usually used to make passive devices in the terahertz frequency band. For filters, better out-of-band rejection is considered to be able to filter out more spurious information to facilitate application in various communication systems. With the development of terahertz technology, the demand for high-performance terahertz filters is also increasing. urgent. The traditional filter can increase its left and right suppression by increasing the order of the filter, which makes the filter need multiple resonant cavities to achieve the required index; but with the increase of the number of resonant cavities, the insertion loss also increases. The increase also greatly increases the size and manufacturing cost of the filter.

Another effective way to improve the frequency selectivity of the filter is to increase the transmission zero near the passband of the filter to make the out-of-band rejection better. In the terahertz frequency band, there are mainly two ways to introduce transmission zeros for cavity filters: one is to introduce transmission zeros by means of cross-coupling, but this structural design is very complicated, the position of the coupling diaphragm is not fixed, and it cannot be flexible To control the transmission zero position, most of them can only be processed along the H cutting and lead to processing errors ^[1] ; another type of transmission zero is introduced through multi-mode or over-mode coupled resonators ^[2] , but often due to excessive high-order mode resonance When the cavities are cascaded, corner chamfering or movement of the diaphragm is required to shape the filter response, which increases the machining error. At the same time, the traditional dual-mode resonator based on TE mode has a large depth-to-width ratio. If the H-plane symmetric processing method is used, the processing method will destroy the waveguide wall current and deteriorate the overall transmission performance of the filter. The structure of the body and the cover plate will easily cause processing errors due to gaps.

Therefore, how to design a terahertz waveguide filter to make it easy to process with excellent out-of-band rejection has become a research hotspot.

[1]Ding J Q,Shi S C,Zhou K,et al.WR-3Band Quasi-Elliptical WaveguideFilters Using Higher Order Mode Resonances[J].IEEE Transactions on TerahertzScience&Technology,2017: 1-8.

[2] Y.Xiao,P.Shan,K.Zhu,H.Sun and F.Yang,"Analysis of a Novel Singletand Its Application in THz Bandpass Filter Design,"in IEEE Transactions onTerahertz Scienc e and Technology,vol.8 , no.3, pp.312-320, May 2018, doi:10.1109/TTHZ.2018.2823541.

SUMMARY OF THE INVENTION

In view of the problems existing in the background art, the purpose of the present invention is to provide an E-plane terahertz waveguide filter based on a novel dual-mode resonator. The waveguide filter innovatively uses TM120 and TE101 dual-mode cavities, which can introduce a zero point through dual-mode resonance, and can adjust the height and width of the cavity to adjust the zero point position and increase the out-of-band suppression of the out-of-band cavity; In addition, the cavity structure is simple, with a small cavity width-depth ratio, and E-surface processing can be used to reduce the processing error.

For achieving the above object, technical scheme of the present invention is as follows:

An E-plane terahertz waveguide filter based on a novel dual-mode resonator, comprising an input waveguide whose central axis is on the same straight line, several diaphragms, several dual-mode resonators, several single-mode resonators, and an output waveguide; The input waveguide is the input end of the filter, and the output waveguide is the output end of the filter. The input waveguide, the output waveguide, the single-mode resonator and the dual-mode resonator are all rectangular waveguides, wherein the diaphragm is arranged on any two adjacent rectangles. between waveguides;

The double-mode resonator is symmetric with respect to the E-plane and the H-plane of the waveguide, and the size satisfies that the electromagnetic wave signal can simultaneously excite the TM120 and TE101 mode resonances when the electromagnetic wave signal is transmitted in the cavity; the size of the single-mode resonator satisfies the electromagnetic wave signal transmission in the cavity. can excite the TE101 mode resonance.

Further, the length of the dual-mode resonant cavity is a, the width is b, and the height is z, and the specific size relationship satisfies the following formula:

为TM120模式的频率，

为TE101模式的频率，c为光速；所述双模谐振腔能产生零点，并且通过改变腔体的尺寸从而相应改变零点的位置。in,

is the frequency of the TM120 mode,

is the frequency of the TE101 mode, and c is the speed of light; the dual-mode resonant cavity can generate a zero point, and the position of the zero point can be correspondingly changed by changing the size of the cavity.

Further, by adjusting the length or width of the diaphragm, the resonant frequencies f ₁ and f ₂ of two adjacent resonant cavities are changed, so as to adjust the coupling coefficient between the resonant cavities, specifically, K=(f ₁ ² -f ₂ ² )/(f ₁ ² +f ₂ ² ).

其中K₀₁为输入波导或输出波导与相邻谐振腔之间的耦合系数。Further, the length of the diaphragm connected to the input waveguide and the output waveguide is determined by the loaded _QL value, where

where K ₀₁ is the coupling coefficient between the input waveguide or the output waveguide and the adjacent resonator.

Further, the smaller the number of the dual-mode resonator cavity, the smaller the insertion loss of the terahertz waveguide filter and the narrower the bandwidth.

Further, the number of the single-mode resonant cavity may be zero or not.

Further, the broad side in the plane parallel to the electric field E plane of the dual-mode resonant cavity is set in the form of a chamfer, which is convenient for processing.

The mechanism of the invention is: based on the principle of double-mode coupling generating zero point, the cavity structure is designed so that the TM120 mode and the TE101 mode are simultaneously excited and resonated in a single cavity. The difference in the distribution of the magnetic field lines in the cavity will cause the two to be distributed in the opposite direction at the output port, so the phase is opposite to generate a zero point, thereby improving the out-of-band suppression performance of the filter.

To sum up, due to the adoption of the above-mentioned technical solutions, the beneficial effects of the present invention are:

1. The present invention proposes a new type of resonant cavity with dual modes, namely TM101 and TE120 modes, which can better achieve out-of-band suppression by introducing transmission zeros through dual modes.

2. The dual-mode resonator designed by the present invention has a rectangular waveguide with the same height protruding upward and downward with respect to the H plane. The structure is simple and easy to simulate. The overall cavity is symmetrical up and down, front and rear, and has a small aspect ratio. , reduce the processing error;

Description of drawings

FIG. 1 is a schematic structural diagram of a terahertz waveguide filter based on a single dual-mode resonator according to the present invention.

FIG. 2 is a distribution diagram of the TM120 and TE101 modes in the dual-mode resonant cavity in the terahertz waveguide filter of the present invention.

FIG. 3 is the E-surface machining cavity assembly of the terahertz waveguide filter according to Embodiment 1 of the present invention.

FIG. 4 is an S-parameter simulation diagram of the terahertz waveguide filter of the present invention.

FIG. 5 is a schematic structural diagram of a terahertz waveguide filter according to Embodiment 1 of the present invention.

FIG. 6 is a schematic structural diagram of a terahertz waveguide filter according to Embodiment 2 of the present invention.

FIG. 7 is an S-parameter simulation diagram of the terahertz waveguide filter in Embodiment 1 of the present invention.

FIG. 8 is an S-parameter simulation diagram of a terahertz waveguide filter in Embodiment 2 of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

An E-plane terahertz waveguide filter based on a single novel dual-mode resonator, the schematic diagram of which is shown in Figure 1, including an input waveguide 1, a first diaphragm 2, a dual-mode input waveguide 1, a first diaphragm 2, and The resonant cavity 3, the second diaphragm 4 and the output waveguide 5; the input waveguide 1, the output waveguide 5 and the dual-mode resonant cavity 3 are all rectangular waveguides;

The dual-mode resonator is symmetrical about the E-plane (referring to the pattern cut plane parallel to the direction of the electric field) and the H plane (referring to the pattern cut plane parallel to the direction of the magnetic field), and the size satisfies that the electromagnetic wave signal resonates in the cavity according to the TM120 and TE101 modes at the same time. , the distribution diagram of the two modes is shown in Figure 2, where (a) is the TM120 mode and (b) is the TE101 mode.

The length of the dual-mode resonant cavity is a, the width is b, and the height is z, and the specific size relationship satisfies the following formula:

为TM120模式的频率，

为TE101模式的频率，c为光速，所述双模谐振腔能产生零点，并且通过改变腔体的尺寸从而相应改变零点的位置，零点的位置主要由两种模式相位的正负以及相对位置共同决定。in,

is the frequency of the TM120 mode,

is the frequency of TE101 mode, c is the speed of light, the dual-mode resonator can generate a zero point, and by changing the size of the cavity, the position of the zero point can be changed accordingly. The position of the zero point is mainly determined by the positive and negative phases of the two modes and the relative position. Decide.

The diaphragm is symmetrically arranged at the center of the plane formed by the broad side and the high side of the dual-mode resonator; the coupling strength between adjacent resonators is controlled by the diaphragm, that is, the length or width of the diaphragm is adjusted to change the two adjacent resonators. The resonant frequencies f ₁ and f ₂ of the body, thereby changing the coupling coefficient, the coupling coefficient k=(f ₁ ² -f ₂ ² )/(f ₁ ² +f ₂ ² ), from which the size of the diaphragm can be determined; and the input waveguide The length of the diaphragm connected to the output waveguide is determined by the loaded _QL value, where

1 is a schematic structural diagram of a terahertz waveguide filter based on a single dual-mode resonant cavity of the present invention. It can be seen from the figure that when the length b of the narrow side is a small value, that is, the depth of the dual-mode resonant cavity is small, The double-mode frequency can be changed by changing the width a or the height z, so that the double-mode resonant cavity has a smaller aspect ratio (b/a), which is convenient for the milling cutter to process from the E surface. Compared with the traditional resonant cavity based on TE high-order mode, this structure requires a larger b-side length to transmit high-order TE mode. With E surface processing.

FIG. 3 is an assembly drawing of the E surface of the structure shown in FIG. 1 , the entire cavity is cut along the center of the E surface, and the assembly drawing is divided into an upper cavity (a) and a lower cavity (b). If the filter includes a plurality of resonant cavities, the b side of each cavity can be kept the same size, and the whole is symmetrical, which is convenient for processing.

FIG. 4 is a simulation diagram of the S-parameter of the filtering effect of the terahertz waveguide of the present invention by a single dual-mode resonant cavity. When the size parameters of the resonator are as follows: b=1.4mm, z=1.48mm, l=0.2mm, w=0.55mm, the input and output are standard WR4 waveguides, A=1.092mm, B=0.546mm, and the chamfers are unified as 0.1mm. Keeping z and b unchanged, and changing the size of side a of the cavity, the resonant position of the TE 101 mode changes and the resonant frequency of the TM120 mode can be fixed at 220 GHz. It can be seen from the figure that a single cavity is a resonance point and a transmission zero point that can generate two different modes, and it can be seen from (a) in Figure 4 that when f _TE101 < f _TM120 , the zero point is generated in the upper sideband, from It can be seen from (b) in Fig. 4 that when f _TE101 > f _TM120 , the zero point is generated in the lower sideband, and the simulation software is HFSS.

Example 1

The structure of the terahertz waveguide filter in this embodiment is shown in FIG. 5 , including an input waveguide 6 , a first diaphragm 7 , a first dual-mode resonant cavity 8 , and a second diaphragm, which are connected in sequence and whose central axes are on the same straight line. 9. The first single-mode resonant cavity 10 , the third diaphragm 11 , the second single-mode resonant cavity 12 , the fourth diaphragm 13 , the second dual-mode resonant cavity 14 , the fifth diaphragm 15 and the output waveguide 16 .

This embodiment is a fourth-order WR-4 filter with two dual-mode cavities, and the S-parameter simulation diagram of the filter is shown in FIG. 7 . It can be seen from the figure that the S-parameter map produces two zeros and six poles on the left and right, the echo is greater than 20B, the external suppression can be 50dB, and it has a good square coefficient. The specific dimensions of the filter are: z_8=1.519mm, z_10=z_12=0.91mm, z_14=1.438mm, a_8=0.639mm, a_10=0.638mm, a_12=0.64mm, a_14=0.689mm, l_7=0.138mm, l_9=0.527mm, l_11=0.512mm, l_13=0.533mm, l_15=0.1mm, w_7=0.573mm, w_9=w_11=w_13=0.55mm, w_15=0.534mm, the diaphragm and the b side of the resonant cavity are the same, that is, unified is b=1.4mm, the input and output are standard WR4 waveguide, that is, A_6=A_16=1.092mm, B_6=B_6=0.546mm, the chamfer is unified to 0.1mm, and the simulation software is HFSS.

Example 2

The structure of the terahertz waveguide filter of this embodiment is shown in FIG. 6 , including an input waveguide, a first diaphragm, a first single-mode resonant cavity, a second diaphragm, a second A single-mode resonant cavity, a third diaphragm, a dual-mode resonant cavity, a fourth diaphragm, a third single-mode resonant cavity, a fifth diaphragm, a fourth single-mode resonant cavity, a sixth diaphragm, and an output waveguide.

The S-parameter simulation diagram of the filter in this embodiment is shown in FIG. 8 . Because the entire design is a fifth-order WR-2.8 filter with a dual-mode cavity, one zero and six poles are generated in the S-parameter diagram, and the left and right out-of-band rejection of the cavity is at 45dB. It also has better out-of-band rejection characteristics.

The above descriptions are only specific embodiments of the present invention, and any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all the disclosed features, or All steps in a method or process, except mutually exclusive features and/or steps, may be combined in any way.

Claims (8)

1. An E-surface terahertz waveguide filter based on a novel dual-mode resonant cavity is characterized by comprising an input waveguide, a plurality of diaphragms, a plurality of dual-mode resonant cavities, a plurality of single-mode resonant cavities and an output waveguide, wherein central axes of the input waveguide, the diaphragms, the dual-mode resonant cavities, the single-mode resonant cavities and the output waveguide are located on the same straight line; the input waveguide is the input end of the filter, the output waveguide is the output end of the filter, the input waveguide, the output waveguide, the single-mode resonant cavity and the dual-mode resonant cavity are all rectangular waveguides, and the diaphragm is arranged between any two adjacent rectangular waveguides;

the dual-mode resonant cavity is symmetrical about an E surface and an H surface of the waveguide, and the size of the dual-mode resonant cavity meets the requirement that TM120 and TE101 modes can be excited to resonate simultaneously when electromagnetic wave signals are transmitted in the cavity; the size of the single-mode resonant cavity meets the requirement that TE101 mode resonance can be excited when electromagnetic wave signals are transmitted in the cavity.

2. The E-plane terahertz waveguide filter of claim 1, wherein the length of the dual-mode cavity is a, the width is b, and the height is z, and the specific dimensional relationship satisfies the following formula:

wherein,

is the frequency of the TM120 mode and,

the frequency of the TE101 mode, and c the speed of light.

3. The E-plane terahertz waveguide filter according to claim 2, wherein the two-mode resonant cavity is capable of generating a zero point, and a position of the zero point is changed by changing a size of the cavity.

4. The E-plane thz waveguide filter according to claim 1, wherein the resonance frequency f of two adjacent resonance cavities is changed by adjusting the length or width of the diaphragm ₁ And f ₂ Thereby adjusting the coupling coefficient between the resonant cavities, specifically,

5. the E-plane terahertz waveguide filter according to claim 1, wherein the length of the diaphragm connected to the input waveguide and the output waveguide is expressed by the formula

Determining that Q is the energy storage/loss, K, of the input or output waveguide ₀₁ Is the coupling coefficient between the input waveguide or the output waveguide and the adjacent resonator.

6. The E-plane terahertz waveguide filter according to claim 1, wherein the smaller the number of the dual-mode cavity bodies, the smaller the insertion loss and the narrower the bandwidth of the terahertz waveguide filter.

7. The E-plane terahertz waveguide filter according to claim 1, wherein the number of single-mode resonators is zero or non-zero.

8. The E-plane terahertz waveguide filter of claim 1, wherein a broadside of a plane of the dual-mode cavity parallel to the E-plane of the electric field is chamfered to facilitate processing.

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